Course Highlights

Chemistry: Challenges and Solutions is an introductory chemistry course consisting of 13 units of online text, 13 half-hour videos, three interactive labs, and a professional development guide. The target audiences are high school and college students, as well as teachers who want to learn more about cutting-edge applications of chemistry—including energy and the environment, biotechnology, and material science.

Demo Dan

Videos are enriched with chemistry demonstrations by Dan Rosenberg of the Harvard University Natural Sciences Lecture Demonstrations Department. "Demo Dan" doesn't just make things go "Boom!"—his segments clearly connect key chemical concepts. Dan not only does things you don't want to do at home but makes chemistry come alive for beginning students.

Course Interactive

Interactive labs engage learners in applications of chemistry to real-life problems. The Running Lab explores biochemical pathways in the human body and lets users see the chemical changes as runners train for a race. The Haber process interactive gives learners the keys to a chemical plant and challenges them to operate it profitably by applying chemistry concepts to a real-world problem. A third interactive, Chemistry Timeline, is a useful roadmap to the development of modern chemistry.

Course Introduction

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Chemistry: Challenges and Solutions teaches general chemistry concepts using real-life challenges in energy, materials development, biochemistry, and the environment. The course zeros in on essential topics that are generally taught in introductory chemistry, providing a strong foundation for learners to pursue further study in science or a liberal education. Videos include dramatic demonstrations of key principles, interviews with scientists who are doing current research related to these fields, animations, and clear explanations. Each video is hosted by a different working chemist - together, they show a diversity of chemistry professionals and the challenges chemistry is addressing for society. The on-line text covers key concepts with clear text and illustrations, while interactive labs provide simulations of chemical processes online.

Unit 1: Matter and the Rise of Atomic Theory—The Art of the Meticulous

Since the first time early humans lit a fire, cooked food, fermented fruit, or flaked a stone axe, we have been manipulating the matter around us. This unit explores how chemistry evolved from adapting materials for practical purposes to a science that systematically offers solutions to the world's challenges. It is a story that will start with Democritus around 400 BCE, taking us through the early Arab chemist, Jābir ibn Hayyān, to the meticulous work of the Middle Age alchemists, and finally to the birth of chemistry as a science during the Age of Enlightenment in the 18th century. In the accompanying video, we explore the Silicon Age, where the goal of manipulating and purifying matter at the atomic scale is making possible today's technological advances such as cell phones and solar panels.

Unit 2: The Behavior of Atoms—Phases of Matter and the Properties of Gases

Fundamentally, chemistry is the science of interacting particles. This unit covers the properties of solids, liquids, and gases in terms of the behavior of invisible particles of matter that interact at the atomic scale. Pressure, volume, temperature, and intermolecular forces are some of the variables that control these interactions and lead to the familiar macroscopic properties of matter. Developing a better understanding of the atomic model through experiments with gases, scientists discovered the Ideal Gas Law, developed phase diagrams, and learned about the properties of supercritical fluids. Today's chemists are exploring new ways to control the interactions of atoms, with the goal of making better hydrogen-powered cars and new technologies for the long-term, underground storage of carbon dioxide to reduce greenhouse warming.

Unit 3: Atoms and Light—Exploring Atomic and Electronic Structure

Using light as a probe, scientists found innovative ways to make inferences about the inner structure of the atom. In this unit, we will follow the gradual change from considering the atom as a single indivisible particle to a later understanding of the atom composed of its constituent subatomic parts, including the electron, the first subatomic particle to be discovered, the proton, and the neutron. This new picture of matter lead to the development of the quantum model of the atom, as well as ways to identify traces of chemical elements, whether on Earth, in the Sun, or in a distant galaxy.

Unit 4: Organizing Atoms and Electrons—The Periodic Table

As scientists discovered more and more chemical elements, they began developing systems to organize the elements by their chemical properties, leading to the modern periodic table. Through its organization, the periodic table makes clear the underlying chemical and physical trends among the elements. These characteristics—reactivity, atomic radius, electronegativity, and density—are linked to the distribution of electrons around the nucleus. The periodic table—undoubtedly the most important and useful document in chemistry—is being continually updated even today as scientists strive to create new, man-made elements in laboratories.

Unit 5: Making Molecules—Lewis Structures and Molecular Geometries

Molecules form when individual atoms create bonds by sharing electrons. Understanding how atoms combine to make molecules allows scientists to predict many of the physical and chemical properties of substances. Since the outermost eight electrons are key to forming compounds, this unit shows how the Octet Rule provides a basis for predicting how atoms may gain, lose, or share electrons to fill the slots in their outer shells. A fundamental understanding of how electrons form bonds leads to the three-dimensional shapes of molecules and has implications in all aspects of chemistry, including drug design.

Unit 6: Quantifying Chemical Reactions—Stoichiometry and Moles

Elements combine in definite ratios, and the results of a chemical reaction can be predicted using balanced chemical formulas along with careful measurements of the amount of reactants. In this unit, we will explore atomic mass, the limiting reactant (the first reactant to be used up), and the yield of a reaction. Quantification of chemical reactions is key to all the practical applications of chemistry, from developing new energy resources to chemical manufacturing.

Unit 7: The Energy in Chemical Reactions—Thermodynamics and Enthalpy

The transfer of chemical energy to heat, light, and kinetic energy is striking in the vibrant display of fireworks, but the transfer of energy is also basic to all chemical reactions. Thermodynamics—the study of how and why energy moves—governs what can happen in a chemical reaction. By applying the laws of thermodynamics, chemists can measure, predict, and control the heat and energy of chemical reactions to help solve problems like making cleaner burning rocket fuels and more efficient engines.

Unit 8: When Chemicals Meet Water—The Properties of Solutions

Solutions are all around us, from the air we breathe, to the blood in our veins, to the steel frames of many buildings. While solutions don't have to be liquids, aqueous, or water-based, solutions are fundamental to life and common in inorganic chemistry: the majority of biochemical reactions happen in aqueous solutions. The formation of a solution depends upon the interactions between the solute (the substance that gets dissolved) and the solvent (the substance that does the dissolving), and in, turn, the interactions of solute and solvent are heavily influenced by their concentrations, temperature, and pressure. Solution chemistry is behind the extraction of materials for a variety of applications, for example, making a great cup of coffee.

Some chemical reactions happen spontaneously, like metal rusting. Other reactions are non-spontaneous and need to absorb energy in order to occur. Using the Second Law of Thermodynamics, the principle of entropy, and the calculation of Gibbs free energy, scientists can predict which reactions will occur, and vary the conditions to make more of the desired products. In equilibrium reactions, both products and reactants are always present. Equilibrium reactions in the human body are essential for life and can be exploited in chemical manufacturing as well.

Unit 10: Acids and Bases—The Voyage of the Proton

Acids and bases result from the movement of a hydrogen ion—a positively-charged single proton, whose electron has been stripped away. The acidity of a solution is based on its concentration of hydrogen ions and is measured on the pH scale. Many reactions must happen in a certain pH range and buffers can help control the pH. This is especially evident in the human body, where the blood acts as a buffer for the many chemical reactions that occur in it. Whether it is manipulating the pH of the soil to control the color of hydrangea flowers or meticulously controlling ingredients to bake the perfect pastry, acid-base chemistry is all around us.

Every portable electronic device is fueled by chemistry, specifically through oxidation-reduction or "redox" reactions. In redox reactions, one compound gains electrons (reduction) and one compound loses them (oxidation). Chemists can set up reactions so that electrons are forced to move in a certain way to create an electrical current. Metals often play a key role in redox reactions, which are essential to all aspects of chemistry, particularly in many biochemical processes.

Unit 12: Kinetics and Nuclear Chemistry—Rates of Reaction

In this unit, we will learn how the rate of a chemical reaction is affected by a number of factors, including temperature and the concentration of reactants at the beginning of the reaction. While the chemical equation may show reactants turning into products as a straightforward, simple arrow, there is much more to that arrow than meets the eye. How exactly do reactants turn into products? Sometimes the answer is simple: Two atoms bump into each other and form a bond. Most of the time, however, the process is much more complex. Controlling rates of reactions has implications for a variety of applications including drug design and preventing corrosion. The latter half of this unit introduces nuclear reactions.

Unit 13: Modern Materials and the Solid State—Crystals, Polymers, and Alloys

Understanding the inter-atomic forces that give structure and properties to different types of solids is essential for the creation of new alloys, the development of useful polymers, and the creation of many other kinds of man-made materials. In this closing chapter, we see chemistry as not only an excellent entry point to predicting how a new material behaves, but also a continuous process of innovation and discovery.